This invention relates to the field of fluid purification, and in particular, to the electrolytic treatment of contaminated water. There are many known methods of treating contaminated water to remove varying degrees of contamination therefrom. The two most common methods of water purification are chemical precipitation and reverse osmosis. It has been known to electrolytically treat polluted water to remove contaminants therefrom. For example, Landreth in U.S. Pat. No. 1,131,067 describes a liquid treatment process in which contaminated liquid is fed through a treating chamber containing multiple electrodes spaced and insulated from each other and so disposed that the liquid passes in a zigzag direction backwardly and forwardly through the chamber between the electrodes. The electrodes are alternately charged and are supplied with an electric current of unspecified nature from a generator. Similarly, U.S. Pat. No. 744,171 to Davis, et al discloses a method for separating oil and similar impurities from water by subjecting the solution to an electrolytic field of unspecified nature produced by iron electrodes which may be arranged so that the water flows past them in a zigzag manner. According to Davis, et al, the oil combines with iron freed from the electrodes to form a separable scum. More recently, Vellas, et al in U.S. Pat. No, 3,192,142 have proposed to pass contaminated water through a multiple electrode coagulation set so designed that the polluted water circulates parallel to electrodes supplied with a rectified pulsating electrical current. According to the patentees, this step has the effect of starting a process of coagulation. The oppositely charged electrodes are disclosed as fabricated from different materials, preferably rustless steel and aluminum and the current to the electrodes is selected to transmit positively charged ions to the solution. So far as I am aware, none of the methods described above have proved adaptable to large-scale treatment of contaminated water.
Other workers have commented on the importance of zeta potential in floc formation. See Thomas M. Riddick Chemical Engineering, June 26, 1961, pages 121-126 and July 10, 1961, pages 141-146. Briefly, zeta potential is a measure of the electro-kinetic charge that surrounds suspended particulate matter. Riddick describes the charges on raw water turbidity as predominately electro-negative and strong enough to cause significant mutual repulsion of the suspended particles. When the zeta potential of suspended colloidal matter is reduced to near zero, plus or minus about 5 millivolts, repulsive forces are eliminated, allowing the colloidal particles to collide with each other whereupon the forces of adhesion, cohesion and mechanical locking result in agglomeration, in turn occasioning formation of a large particle size floc which readily settles out of the solution. While Riddick controls zeta potential of colloidal matter by chemical means, applicant has found that the process and apparatus described herein apparently also has the effect of reducing the zeta potential on suspended colloidal matter so a floc can readily form which entraps virtually all of the suspended matter in the solution being treated.